PROJECT SUMMARY Does education change people?s lives in a way that delays mortality? Or is education merely a proxy for unobserved endowments that promote longevity? Most scholars conclude that the former is true, but new evidence by Behrman et al.?who compare the mortality outcomes of Danish twins who differ on educational attainment?calls this conclusion into question. Unfortunately, Behrman et al.?s potentially field-changing finding?that obtaining additional schooling has no independent effect on survival net of other hard-to-observe characteristics?has not yet been subject to replication in the United States or other non-Scandinavian countries. Nor is there a strong scholarly consensus regarding the use of twin data to identify the causal effect of education on mortality in the general population. To address these and other concerns, we will produce the first U.S.-based estimates of the effects of education on mortality (and any variation in those effects that exists across sub-groups and/or birth cohorts), using a large and representative panel of twins drawn from linked complete-count Census records. For comparison purposes, and to shed additional light on the specific roles that neighborhood, family, and genetic factors play in confounding associations between education and mortality, we will also produce parallel estimates of the education-mortality relationship using data on (1) non-twin pairs who lived in different neighborhoods during childhood; (2) non-twin pairs who shared the same neighborhood growing up; and (3) non-twin siblings who shared the same family environment but whose genetic endowments vary to a greater degree. Findings from this research will have major implications for our understanding of educational gradients in mortality and should provide a useful foundation for future work examining the etiology of human survival.